The name "de Thornton" also appears in the early annals, indicating a Norman ancestry. Thornton in Gaelic was MacSkenaghan or MacScienaghan, from Sceine, a knife.

There are numerous families of Thorntons in the United States. One of the earliest Thornton immigrants to America was William Thornton, who came from Yorkshire, England prior to 1646 and settled in York County, Virginia. This William Thornton was the ancestor of a large number of prominent descendants, some of whom became connected by marriage with the family of President George Washington, as well as President Zachary Taylor. Dr. John H.P. Thornton, who married Mary, daughter of President William Henry Harrison, was probably of this family.

Another early immigrant to America was John Thornton, who was one of the founders of the First Baptist Church of Newport, R.I. in 1648.

Rev. Thomas Thornton, who came from England in 1663 and settled at Yarmouth, Mass, was the ancestor of descendants of eminence.

James Thornton, father of Hon. Matthew Thornton, one of the signers of the Declaration of Independence, emigrated from Ireland to America in 1718.

There were other Thornton families who settled in Massachuesetts, Connecticut, New York, Pennsylvania and Virginia.